字符串反转

  string str="dsf";            char [] array1=str.ToCharArray();            for (int i = 0; i < array1.Length/2;i++ )            {                var temp = array1[i];                array1[i] = array1[array1.Length - 1 - i];                array1[array1.Length - 1 - i] = temp;            }            return new string(array1);